The present invention relates to a high voltage protection circuit as it is used in electronic systems that may be exposed to sudden high voltage spikes. The circuit may be used to protect electronic devices that operate on a relative low voltage but are subject to sudden peak voltages. For example, in an electronic brake system (EBS) of a vehicle, circuitry is designed to operate at or below 40 volts. However, when a load dump or positive transient occurs, the voltage applied to components may greatly exceed the maximum voltage causing failure.
One circuit arrangement for overload protection is shown by U.S. Pat. No. 6,556,401 (Loewen et al.). The overload protection circuit includes a third circuit path. The third circuit path is between the first circuit path and a connection of a field-effect transistor which is coupled to the second input connection, and includes the source/drain path of a second field-effect transistor. The third circuit path is completed if an overload occurs between the first and the second input connection. The gate connection of a field-effect transistor is connected to a potential in the first circuit path between the first input connection. The first output connection, and the gate connection of the second field-effect transistor is connected to a potential in the second circuit path between the second output connection and that connection of the first field-effect transistor which is coupled to the second output connection. However, this system is ineffective in protecting against spikes caused by a load dump or positive transient occurrence.
A second circuit arrangement for overload protection is shown by U.S. Pat. No. 6,411,481 (Seubert). A switch and load are connected in series between the terminals of a voltage source. The switch is triggered to release the current flow in the load if the voltage exceeds a threshold value. This device suffers from needing extra switches causing extra costs and size to the system.
It is therefore an object of the current invention to suggest a circuit design that protects from large voltage spikes, yet is inexpensive to make and small in size. It is a further object of the invention to provide adequate protection with minimal additional components that can be used with current production electronic circuits.